This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows: The primary objective is to determine the accuracy of colour DUS, CT angiography, MR angiography, and contrast-enhanced MR angiography in comparison with intra-arterial angiography in patients with symptoms attributable to carotid stenosis (transient ischaemic attack, minor stroke, retinal artery occlusion, or amaurosis fugax). To reflect clinical practice, the review will consider each of the four index tests used singly, and also colour DUS followed by any of the four index tests. This work is based on an earlier systematic review (Wardlaw 2006). We therefore know that many articles do not report the data needed to investigate the heterogeneity due to differences in the patient population (age, gender, whether the symptom affected the eye or brain), differences in the expertise of the people making the diagnoses, and the time interval between the index and reference tests. We had also investigated generation of technology (using year of publication as a proxy) and did not find evidence that it was a significant source of heterogeneity.